In the panoramic tomographic radiography technique, a layer of certain thickness of the object is visible on the film. This is the so-called picture layer, the form, location and thickness of which can be affected through appropriate planning of the geometry pertaining to the projection of the object. Normally, in this photo technique, the radiation source and the film move in relation to the patient, who thus remains still during the radiographing. The desired point of the object is pictured accurately on the film, if the same speed is chosen for the film and the projection point on the surface of the film of the point to be pictured.
In the presently existing arrangements the layer to be pictured, without exception, is kept steady and the patient's head is moved with the help of head supports, so that the patient's head can be set in the right position in relation to the layer to be pictured.
In panoramic tomographic radiography, the position of the patient in relation to the layer to be pictured is a delicate operation in terms of the final outcome. Even the smallest mistake when positioning the patient will show in the X-ray picture. The weakness of known systems is the fact, that the patient's head has to be positioned correctly and at the same time supported properly during radiography.
The following U.S. patents will give more information about the present level of the technology: U.S. Pat. Nos. 2,684,446; 2,798,958; 3,045,118; 3,521,057; 3,356,913 and 3,636,349.